This invention generally relates to motors and, more particularly, the invention relates to synchronizing DC electric motor operation to a reference frequency.
Many systems utilize multiple D.C. motors in parallel for various reasons. For example, multiple fans are utilized to cool elevators, and many computer systems utilize two or more fans to cool internal electronic components. Such systems often are preconfigured so that the fans are synchronized to operate at a substantially identical rotational speed. In practice, however, although ideally set to operate synchronously, such fans often operate at different speeds. When fans are not synchronized, they often generate a noise that many people tend to consider annoying.
In accordance with one aspect of the invention, a DC electric motor includes an internal programmable element that permits it to be synchronized to an external reference signal. To that end, the motor includes a rotor capable of rotating at a rotational speed, rotor circuitry that controls the rotational speed of the rotor, and an input to receive the noted external reference signal, which indicates a preset speed. In addition, the motor also includes the noted programmable element, which is operatively coupled with the input and the rotor circuitry within the motor. The programmable element is capable of comparing the external reference signal with the rotational speed of the rotor and, consequently, controls the rotor circuitry based upon the comparison of the external reference signal and the rotational speed of the rotor.
The programmable element preferably is a processor. In illustrative embodiments, the programmable element is capable of controlling the rotor circuitry to increase the rotational speed of the rotor if it is determined that the rotational speed of the rotor is less than the preset speed indicated in the external reference signal. In a similar manner, the programmable element also may be capable of controlling the rotor circuitry to decrease the rotational speed of the rotor if it is determined that the rotational speed of the rotor is greater than the preset speed indicated in the external reference signal.
Among other things, the rotor circuitry may include at least one of switching circuitry and commutation circuitry. The motor also may include a housing containing the rotor circuitry and programmable element. In some embodiments, the programmable element is programmed to detect an error condition with the external reference signal. The programmable element consequently sets the rotational speed of the rotor to a selected speed if the error condition is detected. By way of example, the error condition may be considered to have occurred if the preset speed is not within a prescribed range of speeds. The motor also may include an internal clock that produces an internal clock signal. The selected speed thus may be based upon the internal clock signal. The motor may be used as a fan and thus, include an impeller coupled with the rotor.
In accordance with another aspect of the invention, a motor apparatus has a first DC electric motor capable of rotating at a first rotational speed and having a first internal processor, and a second DC electric motor capable of rotating at a second rotational speed and having a second internal processor. In addition, the motor apparatus also includes a master clock that produces a reference signal indicating a preset speed. The master clock is coupled with both the first DC electric motor and the second DC electric motor. In illustrative embodiments, the first processor is capable of controlling the first rotational speed to be synchronized with the reference signal, and the second processor is capable of controlling the second rotational speed to be synchronized with the reference signal.
In some embodiments, the first DC electric motor includes a first impeller, and the second DC electric motor includes a second impeller. The first processor may include a first reference input, and the second processor includes a second reference input. The first and second reference inputs thus may be coupled with the master clock to receive the reference signal. In other embodiments, the first rotational speed and second rotational speed are substantially identical. Moreover, the motor apparatus may include a first motor housing containing the first DC electric motor, and a second motor housing containing the second DC electric motor.
The first DC electric motor may include commutation circuitry that is controlled by the first processor. The first internal processor may be programmed to detect an error condition with the reference signal and, consequently, set the first rotational speed to a selected speed if the error condition is detected. The error condition may be considered to have occurred if the preset speed is not within a prescribed range of speeds. The first internal processor may include an internal clock that produces an internal clock signal. Accordingly, the selected speed may be based upon the internal clock signal.
In accordance with another aspect of the invention, a DC electric motor includes a rotor capable of rotating at a rotational speed, rotor circuitry that controls the rotational speed of the rotor, and a receiving means for receiving an external reference signal indicating a preset speed. In addition, the motor also may include a comparing means for comparing the external reference signal with the rotational speed of the rotor. The comparing means includes means for controlling the rotor circuitry based upon the comparison of the external reference signal and the rotational speed of the rotor. The comparing means preferably is internal to the motor.
In accordance with still another aspect of the invention, a rotor circuit for controlling the speed of a rotor (i.e., the rotor being a part of a DC electric motor) includes switching circuitry that, at least in part, controls the rotational speed of the rotor, and an input for receiving an external reference signal indicating a preset speed. In addition, the rotor circuit also include a programmable element operatively coupled with the input and the switching circuitry. The programmable element compares the speed of the rotor with the preset speed indicated in the reference signal. The programmable element controls the switching circuitry based on the comparison of the preset speed and the speed of the rotor. The switching circuitry and programmable element are internal to the motor.